Microcomputer having built-in nonvolatile memory and check system thereof and IC card packing microcomputer having built-in nonvolatile memory and check system thereof

ABSTRACT

When a built-in nonvolatile memory in a microcomputer is tested, a control program prestored in a boot ROM is run upon entering a test command from an external communication device; a test program is transferred from the external communication device to a built-in RAM through a communication circuit; a control of a CPU is switched to the built-in RAM after the test program has been transferred and a test is conducted on the nonvolatile memory; and a test result and a fail log are transferred to the external communication device through the communication circuit. Consequently, the built-in nonvolatile memory in the microcomputer can be checked without leaving the test program on the chip.

FIELD OF THE INVENTION

The present invention relates to a microcomputer having a built-innonvolatile memory, an IC card packing the same, and a check systemthereof.

BACKGROUND OF THE INVENTION

It is easy to overwrite data or programs written into an at leastpartially erasable built-in nonvolatile memory in a microcomputer byexternal means, such as general memory writer and tester, or internalmeans, such as internal CPU and ROM. For this reason, microcomputershaving built-in nonvolatile memories are used extensively in electricappliances and OA (Office Automation) systems as data memories orprogram memories.

Further, a recent years' remarkable increase in a memory capacityprovides a variety of uses for the microcomputers. Under thesecircumstances, there has been an increasing need for microcomputerswhich can assure safety of human health and ensure higher security.Accordingly, the need for higher reliability of a built-in non-volatilememory in the microcomputer as to the overwritable times, the validityof saved data, etc. has been also increasing.

In order to upgrade the reliability of the microcomputers havingbuilt-in nonvolatile memories, a more accurate test should be conductedon the nonvolatile memories per se, and more importantly, a test shouldbe conducted on the microcomputers as the completed products and furtheron IC cards packing the same.

The following will explain a test conducted on a built-in nonvolatilememory in a conventional typical microcomputer with reference to FIGS. 6and 7.

As shown in FIG. 6, a conventional typical microcomputer 80 comprises anonvolatile memory 81, a RAM 82, a CPU 83, a control circuit 84, and aboot ROM 85, which are interconnected to each other via an internal bus.

In most of the cases, a general logic tester or the like is used to testthe above-arranged microcomputer 80. More specifically, as shown in FIG.7, a plurality of test terminals (terminal group 91) of a general logictester 90 (hereinafter, referred to simply as tester 90) are connectedto a plurality of test terminals (terminal group 86) of themicrocomputer 80 in a one-to-one correspondence. Then, the microcomputer80 is switched to the test mode by a signal from the tester 90, and atest is conducted on the internal circuits.

In this case, the test program is stored in the tester 90, and for thisreason, in order to enable the tester 90 to give a data signal, anaddress signal, a clock signal, a control signal, etc. to themicrocomputer 80, connecting means composed of at least tens of pins isnecessary (FIG. 7).

Thus, this test method using the tester 90 can not be applied whenconducting a final test on the memory section of the completed productprior to shipment. Hence, a final check can be conducted only by aso-called actual test, by which the completed product is actuallyoperated for a check-up. In other words, after the microcomputer 80 ispacked in the product, the check-up items available by the above testmethod are limited to writing, reading, and erasing with respect to thenonvolatile memory 81, and there is a problem that detailed check-upitems, such as a shift quantity of a Vth voltage in each memory cell,can not be tested.

If the microcomputer 80 packed in the product could be connected to thetester 90 through connecting means composed of tens of pins, therearises another problem that the general tester can test only one chip ata time. The most advanced general logic tester can test more than onechip, but the number of chips is limited to a few at most. If thenonvolatile memory 81 is to be tested in detail with high accuracy, thetime required for the test and the number of check-up items areincreased markedly compared with the conventional test method. Thus, itis essential to test a greater number of chips simultaneously to savethe cost of the test.

As has been discussed, one of the most important applications of themicrocomputer having an at least partially erasable built-in nonvolatilememory is the use in an IC card.

The IC card is defined as a card including a information data recordingmemory represented by a nonvolatile memory, and a microcomputer whichcontrols the memory, wherein data and programs are stored in the memorywhile data is read out or written into the memory when necessary.EEPROMs (Electrically Erasable and Programmable Read Only Memories) arewell known as a built-in information data recording memory in the ICcard. Typical EEPROMs have a memory capacity of 8–16 Kbytes and data canbe overwritten up to 10,000 times. However, IC cards having built-inmemories with a capacity increased to hundreds Kbytes to some Mbytes,such as a flash memory and a FERAM (Ferro Electric Random AccessMemory), and ensuring tens to hundreds thousands times of overwritinghave been nearing the practical use.

The IC cards are used in diversified fields including electronicsettlements of accounts, public transportation, medical, distributions,etc. For this reason, not only higher reliability, but also highersecurity against forgery are required for the IC cards.

In order to ensure reliability of the IC card having a built-innonvolatile memory, the test is generally conducted on the chip per se,and another test is conducted further on the memory packed in the card.A generally adopted test method for the memory is as follows. That is, atest program is stored in the built-in ROM or test ROM during themanufacturing process, so that when a test command is entered from anexternal check device, the CPU starts to run the test program on thetest ROM, whereby the test is conducted on the memory.

For example, Japanese Laid-open Patent Application No. 3082/1985(Japanese Official Gazette, Tokukaisho No. 60-3082, publishing date:Jan. 9, 1985) discloses a technique which realizes the test on thememory packed in the IC card. More specifically, an IC card is set in acertain check device and a test command signal is sent to the IC cardfrom the check device, whereupon the CPU starts to run the test programprestored in the built-in ROM, thereby making it possible to conduct atest on the memory packed in the IC card.

Also, Japanese Laid-open Patent Application No. 193056/1985 (JapaneseOfficial Gazette, Tokukaisho No. 60-193056, publishing date: Oct. 1,1985) discloses a similar technique.

However, the above conventional technique essentially uses the testprogram written into the ROM, and therefore, the IC card has toadditionally include the test ROM or secure a program area for the testprogram in the built-in ROM. Thus, because the capacity secured for thetest program is limited, there is a problem that a test can not beconducted in a satisfactory manner to ensure the reliability of thememory.

The number of the tests conducted on the nonvolatile memory should beincreased with the increasing reliability. In particular, in order toensure tens to hundreds thousands times of overwriting, in addition tothe test of writing/reading/erasing with respect to the memory, a testshould be conducted on the writing/reading/erasing margins by checkingthe Vth voltage in each memory cell.

However, the test program written into the ROM can not be overwritten.Thus, if a plurality kinds of test programs need to be written into theROM, a capacity of the ROM has to be increased markedly. Even if acapacity of the ROM is increased, however, the check device and chipcommunicate in a one-to-one correspondence in the final stage. Thus,unlike the burn-in test, a large number of chips can not be tested at atime.

Further, should the chip packed in the IC card be analyzed for forgerywith the today's advanced analysis technique, in case that the programdata is created and written into the ROM during the manufacturingprocess, highly confidential data, such as address information of thenonvolatile memory and Vth data, is readily analyzed by irradiatinglaser beams from the back surface of the wafer, etc. Hence, storing thetest program for the nonvolatile memory in the ROM is virtually exposingthe security of the IC card to danger.

This problem could be solved by replacing the ROM with anothernonvolatile memory for storing the test program, and erasing the testprogram after the test is completed. However, by providing an additionalnonvolatile memory for the use of test alone, not only the chip area isincreased undesirably, but also another test should be conducted on thisadditional nonvolatile memory. This counter method is, therefore, notworthwhile after all.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide amicrocomputer having a built-in nonvolatile memory which can realize acheck-up without leaving a test program on the chip, an IC card packingthe same, and a check system thereof.

In order to fulfill the above and other objects, a microcomputer havinga built-in nonvolatile memory of the present invention is characterizedby being furnished with:

-   -   a communication circuit for receiving a test program for a        nonvolatile memory from an external check system; and    -   a RAM on which the test program is run.

According to the above arrangement, the test program for the nonvolatilememory is sent from the external check system through the communicationcircuit. The test program is run on the RAM, and the nonvolatile memoryis tested in accordance with the test program.

Incidentally, in order to check the built-in nonvolatile memory in themicrocomputer, the test program for the nonvolatile memory isconventionally stored in the built-in ROM or test ROM during themanufacturing process so as to cut the check time shorter and make thecheck system simpler.

However, the above conventional arrangement has a following problem.That is, the program written into the ROM can not be overwritten whereasa number of test programs should be written into the ROM but the ROM hasa limited capacity. Hence, a sufficient number of programs can not bewritten into the ROM, thereby making it impossible to conduct a test ina satisfactory manner to prove high reliability of the nonvolatilememory.

Further, in case that the program data is created and written into theROM during the manufacturing process, the data can be readily analyzed.Thus, the conventional method, that is, storing the test program in theROM, is virtually exposing the security of the IC card to danger.

In contrast, according to the arrangement of the present invention, thetest program for the nonvolatile memory is sent from the external checksystem and run on the RAM. Thus, a number of test programs can betransferred temporarily to the RAM and run thereon without using a ROMin which the test programs has been written in advance. Consequently, ahighly reliable test having a sufficient number of check-up items can beconducted without any restriction from a limited capacity of the ROM.

Further, the test program transferred onto the RAM is erased as soon asthe test is completed and the supply of the power source voltage isstopped. Thus, because the test program is not left in the completedproduct, unauthorized analysis of the test program can be prevented. Theforegoing is particularly effective for a product that requires highreliability and security, such as the IC card packing the microcomputerhaving a nonvolatile memory.

Also, a check system of the present invention of the microcomputerhaving a built-in nonvolatile memory is characterized by being furnishedwith:

-   -   at least one external communication device connected to the        microcomputer in such a manner so as to allow a communication in        a one-to-one correspondence,    -   each external communication device including,        -   a storage device having stored a test program for a built-in            nonvolatile memory in the microcomputer, and        -   a communication microcomputer for sending the test program            to the microcomputer.

According to the above arrangement, the external communication deviceand the microcomputer having a built-in nonvolatile memory are connectedto each other in such a manner so as to allow a communication in aone-to-one correspondence. The external communication device stores thetest program for the built-in nonvolatile memory in the microcomputer,and sends the same to the microcomputer having a built-in nonvolatilememory.

In other words, it is not necessary to write the test program in thebuilt-in ROM or test ROM in the microcomputer having a built-innonvolatile memory in advance, because the test program can be sent fromthe external communication device. Consequently, a highly reliable testhaving a sufficient number of check-up items can be conducted withoutany restriction from a limited capacity of the ROM.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing an arrangement of amicrocomputer having a built-in nonvolatile memory and a check systemthereof in accordance with one embodiment of the present invention;

FIG. 2 is a block diagram schematically showing an arrangement of an ICcard packing the microcomputer having a built-in nonvolatile memory ofFIG. 1 and a check system thereof;

FIG. 3 is a flowchart detailing operations of the microcomputer having abuilt-in nonvolatile memory of FIG. 1 and a check system of a DUT ofFIG. 4;

FIG. 4 is a block diagram schematically showing an arrangement of acheck system of a DUT having a built-in nonvolatile memory in accordancewith another embodiment of the present invention;

FIG. 5 is a block diagram schematically showing a check system of an ICcard module packing the DUT having a built-in nonvolatile memory of FIG.4;

FIG. 6 is a block diagram schematically showing an arrangement of aconventional microcomputer having a built-in nonvolatile memory; and

FIG. 7 is a block diagram schematically showing an arrangement of acheck system of the conventional microcomputer having a built-innonvolatile memory of FIG. 6.

DESCRIPTION OF THE EMBODIMENTS Embodiment 1

Referring to FIGS. 1 through 3, the following description will describeone embodiment of the present invention.

As shown in FIG. 1, a check system of a microcomputer 10 having abuilt-in nonvolatile memory of the present embodiment (hereinafter,referred to simply as microcomputer 10) comprises an externalcommunication device 20 and a control computer 30. A check-up of abuilt-in nonvolatile memory 11 in the microcomputer 10 is conducted byconnecting the external communication device 20 to both themicrocomputer 10 and control computer 30 so as to allow mutualcommunications.

The microcomputer 10 comprises the nonvolatile memory 11, a RAM (RandomAccess Memory) 12, a CPU (Central Processing Unit) 13, a communicationcircuit 14, a control circuit 15, and a boot ROM (Read Only Memory) 16,which are interconnected to each other via an internal bus. Themicrocomputer 10 further comprises a terminal group 17 including a VPPterminal 17 a, a VCC terminal 17 b, a GND terminal 17 c, a RST terminal17 d, a CLK terminal 17 e, and an I/O (Input/Output) terminal 17 f.

The CPU 13 runs a program stored in the boot ROM 16 and RAM 12. Thecommunication circuit 14 and control circuit 15 mainly controlcommunications with the external communication device 20 as to a flowingrate, protocols, etc.

The boot ROM 16 positions (stores) only a program to operate thecommunication circuit 14 in such a manner so as to be run by the CPU 13.More specifically, the boot ROM 16 stores a program for the followingjobs of:

-   -   receiving the test program for the nonvolatile memory 11 from        the external communication device 20 and storing the same in the        RAM 12 at a test command issued from the external communication        device 20;    -   running the test program; and    -   sending a test result to the external communication device 20.

The test program for the nonvolatile memory 11 is transferred to the RAM12 from the external communication device 20, stored in the RAM 12 andrun by the CPU 13 in order to conduct a check-up of the nonvolatilememory 11.

The external communication device 20 comprises a communicationmicrocomputer 21, a communication control circuit 22, a power sourcecircuit 23, and a storage device 25, which are interconnected to eachother via an internal bus. The external communication device 20 furthercomprises a terminal group 24 including a VPP terminal 24 a, a VCCterminal 24 b, a GND terminal 24 c, a RST terminal 24 d, a CLK terminal24 e, and an I/O terminal 24 f.

The external communication device 20 and microcomputer 10 are connectedto each other through the terminal group 17 and terminal group 24 insuch a manner that the terminals in each group are connected to eachother in a one-to-one correspondence. Power is supplied respectivelyfrom the VPP terminal 24 a to the VPP terminal 17 a and from the VCCterminal 24 b to the VCC terminal 17 b, and a clock is supplied from theCLK terminal 24 e to the CLK terminal 17 e. In addition, datacommunication is allowed between the I/O terminals 17 f and 24 f whennecessary.

The communication microcomputer 21 and communication control circuit 22mainly control communications with the microcomputer 10 and controlcomputer 30 as to a communication rate, protocols, etc.

The power source circuit 23 is a power source which supplies a drivingpower to the external communication device 20 and the microcomputer 10connected thereto through the VPP terminals 24 a and 17 a and VCCterminals 24 b and 17 b. In other words, the power necessary for themicrocomputer 10 during the check-up of the nonvolatile memory 11 issupplied from the power source circuit 23 in the external communicationdevice 20. Thus, when the test of the nonvolatile memory 11 is completedand the communication between the microcomputer 10 and externalcommunication device 20 is cut, a power source voltage currentlysupplied from the power source circuit 23 in the external communicationdevice 20 is stopped, whereupon the test program stored in the RAM 12 iserased automatically.

The storage device 25 is a memory which stores the test program for thebuilt-in nonvolatile memory 11 in the microcomputer 10. In order toconduct the check-up of the nonvolatile memory 11, the test program isread out from the storage device 25 and sent to the microcomputer 10.The test program may be sent to the external communication device 20from the control computer 30 and stored temporarily in the storagedevice 25 each time a check-up of the nonvolatile memory 11 isconducted.

Further, the external communication device 20 is controlled by anexternal device, namely, the control computer 30. Alternatively, theexternal communication device 20 may be controlled directly by thecommunication microcomputer 21. Further, a plurality of externalcommunication devices 20 may be connected to one control computer 30, sothat a plurality of microcomputers 10 can be tested simultaneously.

Next, the following will explain an IC (Integrated Circuit) card 1packing the above microcomputer 10 with reference to FIG. 2.

The IC card 1 is furnished with, on its surface, a terminal group 17′connected to the terminal group 17 in the microcomputer 10 in such amanner that the terminals in each group are connected to each other in aone-to-one correspondence. Thus, the external communication device 20 isconnected to the terminal group 17 through connection between theterminals in the terminal group 24 and terminal group 17′ in aone-to-one correspondence, whereby a communication with themicrocomputer 10 is allowed.

Thus, as was with the microcomputer 10, a plurality of the externalcommunication devices 20 may be connected to one control computer 30, sothat a plurality of IC cards 1 can be tested simultaneously.

Next, the following will explain the operations involved in the test onthe microcomputer 10 with reference to the flowchart of FIG. 3. Itshould be appreciated that the operations involved in the test on the ICcard 1 (FIG. 2) are the same.

Initially, the microcomputer 10 is electrically connected to theexternal communication device 20 through the terminal groups 17 and 24(terminal groups 17′ and 24). The electrical connection may beestablished by means of direct physical contact or electric waves, suchas electromagnetic waves, as long as communications are allowed.

When the connection between the microcomputer 10 and externalcommunication device 20 is established, the control microcomputer 30sends a command to the external communication device 20 to start thetransfer of the test program for the nonvolatile memory 11 to themicrocomputer 10 (S1 and S2).

Then, the external communication device 20 sends a signal (command) tothe I/O terminal 17 f of the microcomputer 10 to start the transfer ofthe test program (S3). Upon receipt of the signal (test program transferstart command) (S4), the microcomputer 10 sets the conditions necessaryfor the transfer, such as area allocation in the RAM 12 for thetransferred test program, whereby the microcomputer 10 becomes ready toreceive data (test program).

When the state of the microcomputer 10 to have become ready to receivedata is confirmed, the test program is sent to the microcomputer 10 fromthe external communication device 20 through the I/O terminals 24 f and17 f, and the microcomputer 10 stores the received test program in theRAM 12 (S5 and S6).

The series of operations thus far are carried out by the CPU 13 as itruns the prestored program in the boot ROM 16 in the microcomputer 10.When the transfer of the test program to the RAM 12 is completed, theCPU 13 confirms the completion of the transfer of the test program andswitches the control onto a specific address in the RAM area, and startsto run the test program on the RAM 12 (S7). More specifically, the CPU13 sets the nonvolatile memory 11 to the test mode, completes thecheck-up items one by one, and creates test result data including thetest result, a fail log, etc.

Upon conformation of the completion of the memory test (S8), the CPU 13sends the result data of the memory test to the external communicationdevice 20 which has been waiting for the same (S9, S10, S11). Theexternal communication device 20 makes the pass/fail judgment of thenonvolatile memory 11 based on the result data of the memory test sentfrom the microcomputer 10, and sends the judging result of the memorytest to the control computer 30 which has been waiting for the same(S12, S13, S14). Finally, the test on the nonvolatile memory 11 iscompleted when the control microcomputer 30 receives the pass/failjudgement from the microcomputer 10 (S14).

It should be appreciated that it does not make any difference whetherthe microcomputer 10 makes the pass/fail judgment by the self based onthe test result data which had been created by the self or the controlcomputer 30 does so based on the received test result data.

When the test is completed and the communication between themicrocomputer 10 and external communication device 20 is cut, a powersource voltage currently supplied to the microcomputer 10 from the powersource circuit 23 in the external communication device 20 through theVPP terminals 24 a and 17 a and VCC terminals 24 b and 17 b is stopped,whereupon the test program stored in the RAM 12 is erased automatically.

As has been discussed, the microcomputer having a built-in nonvolatilememory of the present embodiment comprises:

-   -   the communication circuit for transferring the test program from        the external communication device in the check system to the        RAM;    -   the boot ROM enabling the CPU to transfer the test program; and    -   the CPU for switching the nonvolatile memory to the test mode in        accordance with the test program on the RAM.

According to the above arrangement, the nonvolatile memory is switchedto the test mode on the RAM, and consequently, highly reliable andsecure test can be conducted on the built-in nonvolatile memory in themicrocomputer. In other words, by transferring the test program from theexternal to the RAM and conducting a plurality kinds of tests on theRAM, a plurality kinds of tests can be conducted by temporarilytransferring the same on the RAM without using a conventionallyessential exclusive-use ROM having stored the test program.Consequently, a highly reliable test, such as a margin test for thememory cell, can be conducted on the nonvolatile memory.

In addition, the test program transferred onto the RAM is erased as soonas the test is completed and the supply of the power source voltage isstopped. Thus, because the test program is not left in the completedproduct, unauthorized analysis of the test program can be prevented.This is particularly effective for a product that requires highreliability and security, such as the IC card packing the foregoingmicrocomputer having a nonvolatile memory.

Embodiment 2

Referring to FIGS. 4 and 5, the following description will describeanother embodiment of the present invention. Hereinafter, likecomponents are labeled with like reference numerals with respect toEmbodiment 1, and the description of these components is not repeatedfor ease of explanation.

As shown in FIG. 4, a check system of a microcomputer 40 having abuilt-in nonvolatile memory (hereinafter, referred to simply as DUT(Device Under Test) 40) comprises a communication control microcomputer50 (hereinafter referred to simply as microcomputer 50) and a controlcomputer 30. A check-up of the built-in nonvolatile memory 11 in the DUT40 is conducted when paris of the DUTs 40 and microcomputers 50 areprovided on a test board 60 in such a manner that (1) the DUT 40 andmicrocomputer 50 in each pair are connected to each other so as to allowmutual communications, and (2) all the DUTs 40 are connected to onecontrol computer 30 so as to allow mutual communications.

The DUT 40 and microcomputer 50 of the present embodiment are of thesame structures as those of the microcomputer 10 and externalcommunication device 20 of Embodiment 1, respectively.

In the present check system, a plurality of microcomputers 50 and DUTs40 are connected in such a manner so as to allow mutual communicationsin a one-to-one correspondence in each pair, and aligned in parallel onthe test board 60. Each microcomputer 50 is connected to the computer 30in such a manner so as to allow mutual communications individually.

Further, as shown in FIG. 4, the check system is arranged in such amanner that it can additionally conduct a burn-in test by providing theDUTs 40 in a heater block 61. It does not cause any problem if the heatblock 61 is realized by connecting the DUTs 40 and microcomputers 50 toeach other through cables and placing the DUTs 40 in a hot temperaturebath.

FIG. 5 is a view explaining the check system which checks IC cardmodules 41 instead of the DUTs 40 of FIG. 4. Each IC card module 41 isof the same structure as that of the IC card 1 of Embodiment 1.

The check system is arranged in such a manner that it can additionallyconduct a burn-in test by providing the IC card modules 41 in the heaterblock 61. It does not cause any problem if the heat block 61 is realizedby connecting the IC card modules 41 and microcomputers 50 to each otherthrough cables and placing the IC card modules 41 in a hot temperaturebath.

Next, the following will explain the operations involved for the test onthe DUT 40 with reference to the flowchart of FIG. 3. It should beappreciated that the operations involved for the test on the IC cardmodule 41 (FIG. 5) are the same.

The control computer 30 sends a test command to all the microcomputers50 connected thereto simultaneously to start the transfer of the testprogram for the nonvolatile memory 11 to the DUTs 40 (S1). Upon receiptof the test command, each microcomputer 50 processes the command, andconfirms that the received command is the test command (S2).

Upon conformation of the test command, each microcomputer 50 sends asignal (command) to the corresponding DUT 40 to start the transfer ofthe necessary test program (S3). Upon receipt of the signal (testprogram transfer start command) (S4), the DUT 40 sets the necessaryconditions, such as area allocation for the transferred test program onthe RAM 12, whereby it becomes ready to receive data (test program).

When the state of the DUT 40 that it has become ready to receive thedata is confirmed, each microcomputer 50 starts to send the testprogram, and the DUT 40 stores the received test program in the RAM 12(S5, S6). It does not make any difference whether the test program issent from the control computer 30 or the memory (equivalent to thestorage device 25) in each microcomputer 50.

The series of operations thus far are carried out by the CPU 13 as itruns the program prestored in the boot ROM 16 in the DUT 40. When thetransfer of the test program to the RAM 12 is completed, the CPU 13 ineach DUT 40 confirms the completion of the transfer of the test program,and switches the control to a specific address in the RAM area,whereupon the CPU 13 starts to run the test program on the RAM 12 (S7).More specifically, the CPU 13 sets the nonvolatile memory to the testmode, carries out the check-up items one by one, and creates the testresult data including the test result, a fail log, etc.

Upon confirming the completion of the memory test (S8), the CPU 13 sendsthe result data of the memory test to the microcomputer 50 which hasbeen waiting for the same (S9, S10, S11). Each microcomputer 50 makesthe pass/fail judgment of the nonvolatile memory 11 based on the resultdata of the memory test received from the corresponding DUT 40, andsends the judging result of the memory test to the control computer 30which has been waiting for the same (S12, S13, S14). Finally, when allthe DUTs 40 receive the pass/fail judgement, the control computer 30completes the test on the nonvolatile memory 11 (S14).

It should be appreciated that it does not make any difference whetherthe DUT 40 makes the pass/fail judgment by the self based on the testresult data which had been created by the self or the microcomputer 50or control computer 30 does so based on the received test result data.

When the test is completed and the communication between the DUT 40 andmicrocomputer 50 in each pair is cut, the test program transferred ontothe RAM 12 is erased automatically.

As has been discussed, in the check system of the present embodiment ofthe microcomputer having a nonvolatile memory, a plurality of themicrocomputers equivalent to the external communication device ofEmbodiment 1 are aligned in parallel on the same test board, and all themicrocomputers are connected to one system control computer.

In other words, in the check system of the IC card packing themicrocomputer having a built-in nonvolatile memory, a microcomputerdifferent from the external communication device in the check system ofEmbodiment 1 is used as the external communication device, a pluralityof external communication devices are aligned on the same board, and allthe external communication devices are controlled intensively byconnecting the same to another communication device (control computer).Consequently, the check system is arranged in such a manner that aplurality of microcomputers each having a built-in nonvolatile memoryand a plurality of IC cards packing the same are tested simultaneously.

According to the above arrangement, the DUTs and microcomputers alignedon the same test board are controlled intensively, thereby making itpossible to test a plurality of chips simultaneously. Consequently, thecost of the test can be saved markedly.

It should be appreciated that the foregoing descriptions in eachembodiment are not provided to limit the scope of the present invention,and the present invention can be modified in diversified manners asdescribed below, for example.

The microcomputer having a built-in nonvolatile memory in each ofEmbodiments 1 and 2 is a microcomputer having an at least partiallyerasable built-in nonvolatile memory, which may be arranged in such amanner that, when a nonvolatile memory section is tested:

-   -   a control program prestored in the boot ROM is run by entering a        test command from an external communication device;    -   a test program is transferred from the external communication        device to a built-in RAM through a communication circuit;    -   a control of a CPU is switched to the built-in RAM after the        test program has been transferred and a test is conducted on the        nonvolatile memory section; and    -   a test result and a fail log are transferred to the external        communication device through the communication circuit again.

According to the above arrangement, a highly reliable and secure testcan be conducted at a low cost without using a general tester.

The check system of the microcomputer having a nonvolatile memory ineach of Embodiments 1 and 2 may be arranged in such a manner that, whena nonvolatile memory section of the above-arranged microcomputer havinga nonvolatile memory is tested:

-   -   a control program prestored in a boot ROM is run by entering a        test command from an external communication device;    -   a test program is transferred from the external communication        device to a built-in RAM through the communication circuit;    -   a control of a CPU is switched to the built-in RAM after the        test program has been transferred and a test is conducted on the        nonvolatile memory section; and    -   a test result and a fail log are transferred to the external        communication device through the communication circuit again.

According to the above arrangement, a highly reliable and secure testcan be conducted at a low cost without using a general tester.

A check system of the microcomputer having a nonvolatile memory in eachof Embodiments 1 and 2 may be arranged in such a manner that, when anonvolatile memory section of the above-arranged microcomputer having anonvolatile memory is tested:

-   -   a plurality of external communication devices are aligned on the        same board by exploiting the above check system and using        another microcomputer different from the external communication        device;    -   external communication devices are connected to their respective        communication devices, respectively; and    -   all the external communication devices are controlled        intensively.

According to the above arrangement, a plurality of microcomputers eachhaving a built-in nonvolatile memory can be tested simultaneously.

The microcomputer having a built-in nonvolatile memory in each ofEmbodiments 1 and 2 may be packed in an IC card.

A check system of the microcomputer having a nonvolatile memory in eachof Embodiments 1 and 2 may be arranged in such a manner that, when anonvolatile memory section in the above-arranged IC card is tested:

-   -   a control program prestored in a boot ROM is run by entering a        test command from an external communication device;    -   a test program is transferred from the external communication        device to a built-in RAM through a communication circuit;    -   a control of a CPU is switched to the built-in RAM after the        test program has been transferred and a test is conducted on the        nonvolatile memory section; and    -   a test result and a fail log are transferred to the external        communication device through the communication circuit again.

According to the above arrangement, a highly reliable and secure testcan be conducted at a low cost without using a general tester.

A check system of the microcomputer having a nonvolatile memory in eachof Embodiments 1 and 2 may be arranged in such a manner that, when anonvolatile memory section of the microcomputer having a nonvolatilememory packed in the above-arranged IC card is tested:

-   -   a plurality of external communication devices are aligned on the        same board by exploiting the above check system and using        another microcomputer;    -   the external communication devices are connected to the        communication devices, respectively; and    -   all the external communication devices are controlled        intensively.

According to the above arrangement, a plurality of the IC cards eachpacking the microcomputer having a built-in nonvolatile memory can betested simultaneously.

As has been discussed, a microcomputer having a built-in nonvolatilememory of the present invention may comprise:

-   -   a nonvolatile memory;    -   a boot ROM;    -   a RAM;    -   a CPU for running a program stored in the boot ROM and RAM; and    -   a communication circuit for controlling a communication with a        check system,    -   wherein the boot ROM has stored a control program for following        jobs of:        -   receiving a test program for the nonvolatile memory from the            check system and store the same in the RAM at a test command            issued from the check system,        -   running the test program, and        -   sending the test result to the check system.

A check system of the present invention of a microcomputer having abuilt-in nonvolatile memory may include an external communication deviceincluding:

-   -   a storage device having stored a test program for a built-in        nonvolatile memory in the microcomputer;    -   a communication control circuit for controlling a communication        with the microcomputer having a built-in nonvolatile memory; and    -   a communication microcomputer for, when a check-up of the        nonvolatile memory is conducted, sending the test program to the        microcomputer having a built-in nonvolatile memory.

According to the above arrangement, when the nonvolatile memory ischecked, the microcomputer having a built-in nonvolatile memory receivesthe test program for the nonvolatile memory from the check system andstores the same in the RAM in accordance with the control programprestored in the boot ROM at a test command issued from the checksystem, and runs the test program, after which the microcomputer havinga built-in nonvolatile memory sends the test result to the check system.

On the other hand, the check system sends the test command from theexternal communication device to the microcomputer having a nonvolatilememory together with the test program stored in the storage device.

Accordingly, the test program is run after the nonvolatile memory isswitched to the test mode by the test program on the RAM, whereby ahighly reliable and secure test can be conducted. In other words, bytransferring the test program from the external communication device tothe RAM and conducting the test on the RAM, a plurality kinds of testscan be conducted by temporarily transferring the same on the RAM withoutusing a conventionally essential exclusive-use ROM having stored thetest program. Consequently, a highly reliable test, such as a margintest for the memory cell, can be conducted on the nonvolatile memory.

Also, the test program transferred to the RAM is erased as soon as thetest is completed and the supply of the power source voltage is stopped.Thus, because the test program is not left in the completed product,unauthorized analysis of the test program can be prevented. This isparticularly effective for a product that requires high reliability andsecurity, such as the IC card packing the microcomputer having anonvolatile memory.

As has been discussed, the microcomputer having a built-in nonvolatilememory and the check system thereof can conduct a highly reliable andsecure test at a low cost without using the general tester and leavingthe test program on the chip.

If the test as accurate as above is conducted, the number of thecheck-up items is increased markedly. However, the check system isarranged in such a manner that a plurality of external communicationdevices are controlled intensively by the control computer. Thus,because a plurality of microcomputers each having a built-in nonvolatilememory can be tested simultaneously, the cost of the test can be savedsignificantly as an effect.

In other words, the check system of the present invention of themicrocomputer having a built-in nonvolatile memory may comprise:

-   -   a control computer, connected to a plurality of external        communication devices, for intensively controlling        microcomputers each having a built-in nonvolatile memory and        connected to the plurality of the external communication        devices, respectively.

According to the above arrangement, the built-in nonvolatile memories ina plurality of microcomputers are controlled intensively by the controlcomputer, thereby making it possible to check a plurality of chipssimultaneously. Thus, the costs of the check-up of the nonvolatilememory can be saved significantly.

The foregoing effects are especially important for the IC cards eachpacking the microcomputer having a built-in nonvolatile memory of alarge capacity for storing various kinds of information.

An IC card of the present invention may be arranged to pack the abovemicrocomputer having a built-in nonvolatile memory.

In addition, a check system of the IC card packing the microcomputerhaving a built-in nonvolatile memory may comprise an externalcommunication device including:

-   -   a storage device having stored a test program for the built-in        nonvolatile memory in the microcomputer packed in the IC card;    -   a communication control circuit for controlling a communication        with the IC card; and    -   a communication microcomputer for sending the test program to        the IC card when conducting a test on the nonvolatile memory.

According to the above arrangement, in order to conduct a check-up ofthe nonvolatile memory, the microcomputer having a built-in nonvolatilememory packed in the IC card receives the test program for thenonvolatile memory from the check system and stores the same in the RAMat a test command issued from the check system in accordance with thecontrol program prestored in the boot ROM, and runs the test program,after which the microcomputer having a built-in nonvolatile memory sendsthe test result to the check system.

On the other hand, the check system sends the test command to themicrocomputer having a built-in nonvolatile memory packed in the IC cardfrom the external communication device together with the test programstored in the storage device.

Accordingly, a highly reliable and secure test can be conducted byswitching the nonvolatile memory to the test mode by the test program onthe RAM. In other words, by transferring the test program from theexternal communication device to the RAM and conducting the test on theRAM, a plurality kinds of tests can be conducted by temporarilytransferring the same on the RAM without using a conventionallyessential exclusive-use ROM having stored the test program.Consequently, a highly reliable test, such as a margin test for thememory cell, can be conducted on the nonvolatile memory.

Also, the test program transferred to the RAM is erased as soon as thetest is completed and the supply of the power source voltage is stopped.Thus, because the test program is not left in the completed product,unauthorized analysis of the test program can be prevented. This isparticularly effective for a product that requires high reliability andsecurity, such as the IC card packing the microcomputer having anonvolatile memory.

As has been discussed, the IC card packing the microcomputer having anonvolatile memory and the check system thereof can conduct a highlyreliable and secure test at a low cost without using the general testerand leaving the test program on the chip.

The check system of the present invention of the IC card packing amicrocomputer having a built-in nonvolatile memory may be arranged insuch a manner so as to include a control computer, connected to aplurality of external communication devices, for intensively controllinga check-up of the IC cards connected to the plurality of the externalcommunication devices, respectively.

According to the above arrangement, the built-in nonvolatile memories ina plurality of microcomputers packed in the IC cards are controlledintensively by using the control computer, thereby making it possible tocheck a plurality of the IC cards simultaneously. Thus, the cost of thecheck-up of the nonvolatile memory packed in the IC card can be savedsignificantly.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A microcomputer having an at least partially erasable built-in nonvolatile memory including: a communication circuit for receiving a test program for said nonvolatile memory from an external check system; a RAM on which said test program is run; and a boot ROM comprising a control program for, upon receiving a test command issued by the external check system, enabling said receiving of said test program from said external check system using said communication circuit and running of said test program on said RAM, wherein said boot ROM is detached from said nonvolatile memory.
 2. The microcomputer of claim 1, further comprising a plurality of microcomputers each having a built-in nonvolatile memory, and wherein said check system comprises a control computer connected to a plurality of external communication devices, for intensively controlling a check-up of said plurality of microcomputers each connected to said plurality of external communication devices, respectively, and each of said plurality of microcomputers including a boot ROM comprising a control program for, upon receiving a test command issued by the control computer, enabling receiving of said test program from said control computer through a communication circuit and running of said test program on said RAM.
 3. The microcomputer of claim 1, wherein enabling said receiving of said test program performed by the control program of said boot ROM comprises allocating an area on said RAM sufficient to receive the test program and controlling said communication circuit to receive and transmit the test program to said RAM.
 4. A microcomputer having an at least partially erasable built-in nonvolatile memory including: a nonvolatile memory; a boot ROM, wherein said boot ROM is detached from said nonvolatile memory; a RAM; a CPU for running a program stored in said boot ROM and RAM; and a communication circuit for controlling a communication with a check system, said boot ROM having stored a control program for jobs of: upon receiving a test command issued from said check system, receiving a test program for said nonvolatile memory from said check system to be stored in said RAM; running said test program; and sending a test result to said check system.
 5. The microcomputer of claim 4, further comprising a plurality of microcomputers having a built-in nonvolatile memory, and wherein said check system comprises a control computer connected to a plurality of external communication devices, for intensively controlling a check-up of said plurality of said microcomputers each connected to said plurality of external communication devices, respectively, and each of said plurality of microcomputers including a boot ROM having stored a control program for jobs including upon receiving a test command issued from said control computer, receiving said test program for said nonvolatile memory from said check system to be stored in said RAM.
 6. The microcomputer of claim 4, wherein said receiving of said test program performed by the control program stored in said boot ROM comprises allocating an area on said RAM sufficient to receive the test program and controlling said communication circuit to receive and transmit the test program to said RAM.
 7. A check system of an at least partially erasable built-in nonvolatile memory in a microcomputer furnished with: at least one external communication device connected to said microcomputer in such a manner so as to allow a communication in a one-to-one correspondence, each external communication device including, a storage device having stored a test program for said built-in nonvolatile memory in said microcomputer, and a communication microcomputer for sending said test program to said microcomputer, wherein said microcomputer includes a boot ROM comprising a control program for, upon receiving a test command issued by the corresponding external communication device, enabling receiving of said test program from said corresponding external communication device using a communication circuit and running of the test program on a RAM, and wherein said boot ROM is detached from said nonvolatile memory.
 8. The check system of claim 7, further furnished with a control computer, connected to a plurality of external communication devices, for intensively controlling a check-up of a plurality of microcomputers each having a built-in nonvolatile memory and connected to said plurality of external communication devices, respectively.
 9. The check system of claim 8, wherein each of said plurality of microcomputers including a boot ROM comprising a control program for, upon receiving a test command issued by said control computer, enabling receiving of said test program from said control computer through a communication circuit and running of said test program on said RAM.
 10. The check system of claim 7, wherein enabling said receiving of said test program performed by the control program of said boot ROM comprises allocating an area on said RAM sufficient to receive the test program and controlling said communication circuit to receive and transmit the test program to said RAM.
 11. A check system of an at least partially erasable built-in nonvolatile memory in a microcomputer furnished with an external communication device including: a storage device having stored a test program for said microcomputer having said built-in nonvolatile memory; a communication control circuit for controlling a communication with said microcomputer; and a communication microcomputer for sending said test program to said microcomputer when checking the built-in nonvolatile memory therein, wherein said microcomputer includes a boot ROM comprising a control program for, upon receiving a test command issued by the external communication device, enabling receiving of said test program from said external communication device using a communication circuit and running of the test program on a RAM, and wherein said boot ROM is detached from said nonvolatile memory.
 12. The check system of claim 11, further furnished with a control computer, connected to a plurality of external communication devices, for intensively controlling a check-up of a plurality of microcomputers each having a built-in nonvolatile memory and connected to said plurality of external communication devices, respectively.
 13. The check system of claim 12, wherein each of said plurality of microcomputers including a boot ROM comprising a control program for, upon receiving a test command issued by said control computer, enabling receiving of said test program from said control computer through a communication circuit and running of said test program on said RAM.
 14. The check system of claim 11, wherein enabling said receiving of said test program performed by the control program of said boot ROM comprises allocating an area on said RAM sufficient to receive the test program and controlling said communication circuit to receive and transmit the test program to said RAM.
 15. An IC card packing a microcomputer having an at least partially erasable built-in nonvolatile memory including: a communication circuit for receiving a test program for a nonvolatile memory from an external check system; a RAM on which said test program is run, and a boot ROM comprising a control program for, upon receiving a test command issued by the external check system, enabling said receiving of said test program from said external check system using said communication circuit and running of said test program on said RAM, wherein said boot ROM is detached from said nonvolatile memory.
 16. An IC card packing a microcomputer having an at least partially erasable built-in nonvolatile memory including: said at least partially erasable nonvolatile memory; a boot ROM, wherein said boot ROM is detached from said nonvolatile memory; a RAM; a CPU for running a program stored in said boot ROM and RAM; and a communication circuit for controlling a communication with a check system, said boot ROM having stored a control program for jobs of: upon receiving a test command issued from said check system, receiving a test program for said nonvolatile memory from said check system to be stored in said RAM; running said test program; and sending a test result to said check system.
 17. A check system of an IC card packing a microcomputer having an at least partially erasable built-in nonvolatile memory furnished with: at least one external communication device connected to said microcomputer packed in said IC card in such a manner so as to allow a communication in a one-to-one correspondence, each external communication device including, a storage device having stored a test program for said built-in nonvolatile memory in said microcomputer, and a communication microcomputer for sending said test program to said IC card, wherein said microcomputer includes a boot ROM comprising a control program for, upon receiving a test command issued by the corresponding external communication device, enabling receiving of said test program from said corresponding external communication device using a communication circuit and running of the test program on a RAM, and wherein said boot ROM is detached from said nonvolatile memory.
 18. The check system of claim 17, further furnished with a control computer, connected to a plurality of external communication devices, for intensively controlling a check-up of a plurality of IC cards connected to said plurality of external communication devices, respectively.
 19. A check system of an IC card packing a microcomputer having an at least partially erasable built-in nonvolatile memory furnished with an external communication device including: a storage device having stored a test program for said built-in nonvolatile memory in said microcomputer packed in said IC card; a communication control circuit for controlling a communication with said IC card; and a communication microcomputer for sending said test program to said IC card when checking said built-in nonvolatile memory, wherein said microcomputer includes a boot ROM comprising a control program for, upon receiving a test command issued by the external communication device, enabling receiving of said test program from said external communication device using a communication circuit and running of the test program on a RAM, and wherein said boot ROM is detached from said nonvolatile memory.
 20. The check system of claim 19, further furnished with a control computer, connected to a plurality of external communication devices, for intensively controlling a check-up of a plurality of IC cards connected to said plurality of external communication devices, respectively. 